Abstract:Soil organic phosphorus(P) is an important component of the soil P pool and its mineralization plays an important role in global P cycling. Understanding the mineralization of soil organic P is beneficial for the efficient utilization and management of P in terrestrial ecosystems. In recent years, the application of advanced techniques such as modern spectroscopy, chromatography, and mass spectrometry has provided crucial avenues for a more comprehensive characterization of the composition and structure of organic P. This review summarizes the applications of these technologies in quantifying changes in soil organic P content. Organic P, following mineralization, is converted into inorganic P(Pi), making it available for direct uptake and utilization by plants and microorganisms. Soil organic P mineralization is orchestrated by two primary pathways: enzymatic and mineral-mediated processes. Delving into the mechanisms of biological catalysis and abiological mineral-mediated catalysis is crucial for elucidating the control pathways of organic P. The mechanisms of soil organic P mineralization can be divided into biological mineralization driven by the oxidation of organic matter by microorganisms (phoA, phoD, and phoX) in response to energy demand, and biochemical mineralization driven by the release of Pi nutrients from plants in response to the demand for P nutrients mediated by phosphatases. Recent investigations have underscored the significance of minerals as an abiological mineralization pathway, shedding light on the mechanisms and actions of mineral-mediated catalysis. The surfaces of minerals (such as iron (hydro) oxides, manganese (hydro) oxides, and aluminum(hydro)oxides)provide an enzyme-like environment, facilitating the cleavage of phosphate ester (P-O-C) and terminal phosphoanhydride(P-O-P)bonds, resulting in the hydrolysis of organic P to Pi. In soil ecosystems, the biogenic elements carbon(C) and nitrogen(N) are intimately linked with soil organic P mineralization. From a nutrient factor perspective, elucidating the driving patterns of organic P mineralization can inform strategies to regulate soil P pools. Specifically, C effectively drives microbial mineralization of organic P, whereas N influences enzymatic metabolism, with the interplay between the two elements profoundly influencing the soil organic P mineralization process. The multiple forms of organic P present in soils are susceptible to influences from various external factors, which modulate phosphatase activity and alter organic P content, thereby further affecting the mineralization process. Various factors, including agricultural practices (such as fertilizer application, tillage practices, and biochar application), soil physical and chemical properties (such as pH, temperature, soil water content, and soil aeration status), microbial biomass, soil CO2 concentration, vegetation, and pollutants all impact soil organic P mineralization, resulting in corresponding environmental ecological effects. Therefore, regulating organic P mineralization is crucial for enhancing soil fertility and protecting the environment. Future strategies can focus on enhancing phosphatase activity, altering organic P composition, and increasing the abundance of phosphorus-solubilizing microorganisms to improve soil organic P mineralization. This review summarizes the advances in soil organic P mineralization research, synthesizing the soil processes, influencing factors, and control pathways, and highlighting the existing challenges and prospects.

Abstract:Soil organic phosphorus (Po) is an important phosphorus pool in soils. The forms, contents and bioavailability of Po change significantly with pedogenesis, which affects soil P supply, nutrient balance and ecosystem productivity. However, compared with inorganic phosphorus (Pi), previous studies paid less attention to Po, which was mainly attributed to the difficulty in the extraction, analysis and identification of different Po speciation. In recent years, the solution 31P nuclear magnetic resonance (31P NMR) spectroscopy was increasingly applied in pedology for characterizing Po compounds, providing a new way for quantitative analysis of Po forms and contents. This significantly improved our understanding of the transformation process of Po during long-term terrestrial ecosystem evolution. This paper systematically summarized the forms and properties of soil Po, and described the principle and procedures of solution 31P NMR spectroscopy for characterizing soil Pospeciation. Then we reviewed the evolution trends and controls of different Pospeciation during natural pedogenesis, and put forward several questions that need to be resolved in the future. Future research priorities include (i) determining the rates, pathways and thresholds of soil Po transformation during long-term soil evolution; (ii) elucidating the coupling relationship between Po and other nutrients such as C and N at different stages of soil evolution and the mechanisms of fixation and release of soil Po; and (iii) building a quantitative model of Po evolution in different types of soils. Providing solutions to the above questions can improve our understanding of the phosphorus biogeochemical cycle in Earth’s Critical Zone and provide a theoretical basis for nutrient management and regulation at different stages of soil evolution, and would promote sustainable utilization of soil resources.

Abstract:[Objective] Interrill erosion is a complex process triggered jointly by a number of influencing factors, and the effects of each factor vary with changes in other factors.[Method] Based on the data published and available in the literature and multiple linear regression analysis, the effects of soil type, rainfall intensity, slope gradient and slope length on interrill erosion process and the interactions were quantitatively analyzed.[Result] Results show that rain intensity, slope gradient, interrill erodibility and slope length were the main factors contributing to interrill erosion rate positively, and among the factors, rain intensity was the major one, contributing (62.93%). Analysis of the interactions between these factors shows that the increase in slope length promoted the contribution of the factor of slope gradient, but inhibited the contribution of the factor of rain intensity. The increase in slope gradient promoted first and then inhibited the contribution of the factor of slope length, but did reversely the contribution of the factor of rain intensity. The slope gradient of 20% was the inflection point of the interaction between slope length and rain intensity, changing from positive to negative. The increase in rainfall intensity interacted positively with slope length and slope gradient. However, slope gradient was more dependent on rainfall intensity than slope length.[Conclusion] During the process of interrill erosion, the interactions observed between the factors of soil type, rainfall intensity, slope gradient and slope length were either positive or negative. All the findings in this study are of great significance for revealing mechanism of rill erosion and predicting soil erosion on slopes.

Abstract:It is of great significance to compare exotic plants with their respective indigenous plants in growth and effect on soil properties for studies on mechanism of their successful invasion. Subtropical and tropical soils are often strongly weathered and hence low in phosphorus availability. Why can invasive plants, such as Wedelia trilobata, successfully invade South China, where the soil is deficient in phosphorus? An answer to this problem is of great significance for exploration of mechanism of the invasive plants flourishing in infertile soils. However, so far few reports on this topic have been found in the literature. This paper laid its focuses on soil organic phosphorus mineralization, and activities of acid phosphomonoesterase and alkaline phosphomonoesterase in the soils under W. trilobata, native plant W. chinensis and their hybrid in South China. A controlled field experiment using randomized complete block design was laid out in July 2016. The plots in the experiment were planted with W. trilobata, native plant W. chinensis and their hybrid, separately for comparison between the plots in microbial biomass phosphorus, activity of acid and alkaline phosphomonoesterase and soil organic phosphorus mineralization, and for analysis of underlying mechanisms of any possible differences. Results show that Treatment WT (W. trilobata) was higher than Treatment WC (W. chinensis) in soil dissolved organic carbon. In all the three treatments Labile-P accounted only for 2.2%~6.3% of the soil total phosphorus. Treatment WT and Treatment H (hybrid) was higher than Treatment WC in Labile-P, but lower in organic phosphorus, residual phosphorus, total phosphorus and microbial biomass phosphorus. Microbial biomass phosphorus made up 14.3%, 41.2% and 25.7% of the total phosphorus in Treatments WT, WC and H, respectively. The ratio of soil total carbon to organic phosphorus reached well beyond 200, indicating that soil phosphorus was a major limiting factor in the studied region. Soil organic phosphorus, as an important fraction in soil total phosphorus, accounted for 28.7%, 17.6% and 25.0% of the total phosphorus in Treatments WT, WC and H. Correlation analysis shows that Labile-P was significantly and positively related to alkaline phosphomonoesterase, but negatively to alkaline phosphomonoesterase. Treatments WT and H were higher than Treatment WC in activity of alkaline phosphomonoesterase, but did not differ much in activity of acid phosphomonoesterase. So, changes in organic phosphorus fractions were mainly driven by alkaline phosphomonoesterase. The findings suggest that both the invasive and native plants suffer from phosphorus deficiency, and alkaline phosphomonoesterase decomposing soil organic phosphorus may be the major mechanism of the invasive plants adapting to phosphorus limitation in the region. It is expected that this study may help understand the general rule of plant invasion in habitats poor in resource from the new perspective of soil organic phosphorus mineralization.

Abstract:Some problems eoncerning fractionatian of organic phosphorus in acid paddy soils using the Bowman-Cole methcd were studied and a modified sequential fractionation scheme was proposed. Four organic phosphorus fractions were identified as follows.